The present invention generally relates to rotating electrical machines, and more particularly to a device and method for retaining diode lead wires to prevent mechanical failure when the lead wires are subject to centrifugal forces.
Rotating electrical machines, such as motors and generators, are well known in the art. In recent years, numerous designs of these electrical machines have been proposed to reduce the size and cost of these machines. One of the most popular prior art designs include adding to the device a rectifier assembly.
While many of the prior art approaches to reduce the size and cost of the machine have been found satisfactory for their intended applications, the new designs added further disadvantages to the machine.
Basically, in a rectifier assembly, diodes are mounted to a heat sink that is attached to the rotor. Generally, there is either three diodes or six diodes mounted on the heat sink to provide the half wave or full wave rectification. The diode lead wires are fed through openings in the exciter core and attached to the diodes. The diodes can be mounted in several different arrangements, for example: an axial arrangement where the centerline of the diodes is parallel to and radially outward from the centerline of the rotor shaft; a perpendicular arrangement where the centerline of the diodes is at right angles to and radially outward of the centerline of the rotor shaft; and an angular arrangement where the centerline of the diodes is somewhere between parallel to and perpendicular to the centerline of the rotor shaft. The axial arrangement generally results in a smaller, lighter package and, therefore, is a desirable and frequently required mounting arrangement
On axial mounted diodes, the leads are attached using a bolt, nut, washer, and flat washer. The length of the leads between the core opening and the diode connection varies, but they are always acted on by centrifugal forces created by the rotor rotation. Unfortunately, this type of assembly is subject to mechanical failure from the bending moment applied to the lead of the diode resulting from the centrifugal force generated by the rotor rotation.
The length of these leads is not mechanically supported and is subject to stress from centrifugal forces when the machine is in operation as well as forces from angular acceleration and deceleration and vibration of the electrical machine, including rotational vibration. Thus, it is imperative to restrain the leads to prevent the centrifugal forces from deforming or breaking the diode connection.
The prior art restrains the length of the leads by tying them to the rotor shaft with a lacing cord made of NOMEX® impregnated with epoxy. Unfortunately, this method often fails to hold the leads in place due to the expansion of the lacing cord in view of the same centrifugal forces acting on the leads.
As can be seen, there is a need for a structure which will mechanically support the diode lead wires during the operation of the electrical machine. Such a structure should be simple in design and relatively low cost in manufacture.